DatabaseMetaData.getProcedures and getProcedureColumns could throw an exception if a user defined class is not available.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5874 e6896862-9d19-0410-bfb3-e9fa5d50e656
In the server mode, when reading from a CLOB or BLOB, if the connection was closed, a NullPointerException could be thrown instead of an exception saying the connection is closed.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5875 e6896862-9d19-0410-bfb3-e9fa5d50e656
Improved error messages.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5876 e6896862-9d19-0410-bfb3-e9fa5d50e656